Assessing the effectiveness of marine CO 2 disposal

Abstract

We consider the relative effectiveness of systems for collection and marine disposal of CO 2 from fossil fuel fired power plants using comparisons of the trend with time of CO 2 concentration in the atmosphere from systems with and without marine disposal. The retention time for CO 2 increases rapidly with depth of disposal, from a few years in the mixed layer up to several centuries as the depth increases beyond 1000 m, suggesting that deep oceans should be considered as potential storage sites for CO 2. However, CO 2 collection and disposal consumes energy and produces extra CO 2. We show that some of this extra this CO 2 reaches the atmosphere, so that atmospheric concentrations from systems with marine disposal ultimately exceed those from systems without controls. In some circumstances they do so rapidly, making marine disposal less favorable than direct atmospheric release. Global Warming Potential can be used to compare systems. This highlights the difficult issues involved in determining what time scales are important in considering options to reduce concerns about global warming.